Optical recording medium and recording method for the same

ABSTRACT

A main information area  31  capable of recording an information signal and a subsidiary information area  32  for recording subsidiary information that is different from the information signal are divided in one principal plane direction of a substrate, and an information layer for recording the information signal in the main information area  31  is provided also in the subsidiary information area  32 , and medium identification information for distinguishing the medium optically is recorded in the information layer of the subsidiary information area  32  without changing the shape of the information layer. As a result, the medium identification information can be recorded in an optical recording medium  1  stably. In particular, the initialization of a phase change type optical recording medium and the recording of the medium identification information can be performed at the same time, so that the production process can be simplified, and the production costs can be reduced.

TECHNICAL FIELD

The present invention relates to an optical recording medium and amethod for recording information in the optical recording medium.

BACKGROUND ART

In recent years, the amount of information to be recorded in a singleoptical recording medium has been increasing, and the distribution ofinformation recorded in optical recording media as software informationhas been promoted. The technology to prevent illegal copying thereofalso has developed. Therefore, as so-called security measures,identification information is desired to be recorded respectively inoptical recording media.

To meet this requirement, the technique generally applied to recordidentification information for optical recording media is, for example,to provide a pit part of a reproduction-only type optical recordingmedium with an additional area (Burst Cutting Area, hereinafterabbreviated as “BCA”) where bar-codes are overwritten, so thatidentification information (ID) and, if necessary, an encryption key ora decryption key can be recorded in the BCA during the manufacturingprocess of optical recording media.

One example of recording signals in this BCA of a reproduction-only typeoptical recording medium is illustrated in FIG. 14. Specifically, asshown in FIG. 14 (1), based on signals modulated according topredetermined identification information such as ID, a pulse-like laserbeam is emitted in accordance with a pattern of the BCA so as to breakand remove the reflection film of the optical recording medium at astretch in a stripe form as illustrated in FIG. 14 (2). The stripe-formBCA is formed on the optical recording medium with portions where thereflection film is broken and removed and with portions where thereflection film remains, as shown in FIG. 14 (3). When this stripe-formBCA pattern is reproduced by an optical head of an optical informationrecording/reproduction device, the modulated signals show a waveform inwhich some portions are missing intermittently, since the reflectionfilm has been removed in the BCA part. These missing portions in thewaveform then undergo a filter process as shown in FIG. 14 (5), and thedigital reproduction data are detected as shown in FIG. 14 (6). In thisway, the identification information recorded on the optical recordingmedium can be obtained. By reading this identification information, eachoptical recording medium can be specified.

On the other hand, optical recording media are getting diversified moreand more, and not only recording-type optical information recordingmedia provided with an information layer capable of recordinginformation signals have been developed, but also rewritable-typeoptical information recording media provided with an information layercapable of rewriting information signals freely. Since information canbe recorded freely in this recording-type optical information recordingmedium as well as in this rewritable-type optical information recordingmedium (hereinafter referred to as an “optical disc” for both recording-and rewritable-types), it has become increasingly important to take thesecurity aspect of information recorded in optical discs intoconsideration.

However, when the method for forming a BCA pattern by breaking andremoving a reflective layer in a reproduction-only type opticalrecording medium is to be applied to an optical disc, the followingproblems arise.

First, in the information layer containing one of photoactive materialsselected from pigment, magnetic materials and phase change typerecording materials, the presence of information is detected by anoptical change of the information layer itself. Therefore, even if theoptical disc is provided with the reflective layer, an opticaldifference hardly can be detected by the BCA pattern in which only thereflective layer is removed. Thus, it is necessary to generate anoptically detectable change of the information layer itself that canrecord information signals in optical discs.

Next, even if the method for forming a BCA pattern in areproduction-only type optical recording medium is applied by emitting alaser beam pulse-like in accordance with the BCA pattern so as to breakand remove the information layer in the optical disc, it is not possibleto selectively break and remove only the information layer containing aphotoactive material, since a laminated film such as an enhancementlayer, a hard layer, an intermediate layer, or a dielectric layer isformed at least on one side of the information layer. As a result, theinformation layer and/or the laminated film in the vicinity of theboundary of the BCA pattern may be separated, or particle of theinformation layer and/or the laminated film arising inside the BCApattern may cause distortion in forming the BCA pattern part, whichleads to the problem that BCA signals cannot be obtained sufficientlydue to noise mixed in the signals for detecting the BCA.

Furthermore, the defect caused by the separation of the informationlayer and/or the laminated film in the vicinity of the BCA pattern isnot confined to the subsidiary information area but reaches theinformation layer and/or the laminated film of the main informationarea, which is a critical problem for the recording-type opticalrecording medium.

In particular, in the phase change type optical disc, after a light beamwith a pulse modulated according to the information signal is emitted tothe information layer to melt the information layer, the informationlayer is cooled, and thus, a recording mark is formed, so thatinformation is recorded. Since the process of melting the informationlayer is included herein, for the purpose of suppressing the phenomenonof the pulsation or the float of the photoactive material of theinformation layer in the molten state, which causes changes in therecording characteristics, the configuration of providing theinformation layer with a material generally referred to as a dielectric,which has better thermomechanical characteristics than the materialscomprising the information layer, is adopted in which the dielectric ispresent by contacting the information layer. Furthermore, the rewritabletype optical disc in which the phase state changes reversibly has theconfiguration of holding the information layer between dielectrics.

The laminated film having the function of suppressing the phenomenonsuch as the pulsation and/or the float of the photoactive material inthis information layer at the time of melting acts to hinder theformation of a BCA pattern when the BCA pattern is formed. If highenergy is emitted forcibly to form a BCA pattern, due to the lack of theplace for absorbing the impact such as boiling or evaporation of thephotoactive material, the laminated film and/or the information layermay be separated, or bubbles, depressions and particles of the materialof the information layer and/or the laminated film may be created insidethe BCA pattern and in the peripheral portion thereof. Accordingly, thedefect spreads to the subsidiary information area and also to theinformation layer in the main information area, thereby increasing thefactors of causing critical defects that make it impossible to record.

Thus, it is difficult to record BCA patterns that can be detectedexactly at least in the recordable type optical disc. One of the mainreasons for the increase in the manufacturing costs of optical discs isthe problem related to the formation of BCA patterns.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a method forrecording a BCA stably in a recording type optical disc and also toprovide an optical disc in which a BCA pattern is formed.

To solve the above problems, an optical recording medium of the presentinvention is a medium provided with a main information area capable ofrecording an information signal and a subsidiary information area forrecording subsidiary information that is different from the informationsignal, which are divided in one principal plane direction of asubstrate, wherein an information layer for recording the informationsignal in the main information area is provided also in the subsidiaryinformation area, and medium identification information fordistinguishing the medium optically is recorded in the information layerof the subsidiary information area without changing the shape of theinformation layer.

Furthermore, a recording method of an optical recording medium of thepresent invention uses an optical recording medium provided with a maininformation area capable of recording an information signal and asubsidiary information area for recording subsidiary information that isdifferent from the information signal, which are divided in oneprincipal plane direction of a substrate, wherein an information layerfor recording the information signal in the main information is providedalso in the subsidiary information area, and medium identificationinformation for distinguishing the medium by an optical phase change isrecorded in the information layer of the subsidiary information area.The recording method comprises: recording medium identificationinformation optically in the information layer of the subsidiaryinformation area, and recording an information signal optically in themain information area, wherein the medium identification information isrecorded first and the information signal is recorded afterwards with amodulation method that is different from a light beam modulation methodused for recording the medium identification information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one example of a recording device ofthe present invention.

FIG. 2 is a cross-sectional structural view of an important part in anexample of an optical disc applicable to the present invention.

FIG. 3 is a top view showing an example of an optical disc applicable tothe present invention.

FIG. 4 is a flow chart showing an example of a method for recordingmedium identification information of the present invention.

FIG. 5 is a view showing a timing chart in an example of a method forrecording medium identification information of the present invention.

FIG. 6 is a view showing an example of a method for recording mediumidentification information of the present invention.

FIG. 7 is a top view showing the above recording method.

FIG. 8 is a block diagram showing another example of a recording deviceof the present invention.

FIG. 9 is a flow chart showing another example of a method for recordingmedium identification information of the present invention.

FIG. 10 is a flow chart of the above recording method.

FIG. 11 (1) to 11 (3) are views each showing an example of a wave formchart of a laser output in another example of recording mediumidentification information of the present invention, wherein

FIG. 11 (1) is a wave form chart of a laser output when mediumidentification information is recorded.

FIG. 11 (2) is a wave form chart of a laser output during a phaseconversion process; and

FIG. 11 (3) is a wave form chart of a laser output when mediumidentification information is recorded and the phase conversion processis performed at the same time.

FIG. 12 is a flow chart showing yet another example of a method forrecording medium identification information of the present invention.

FIG. 13 is a flow chart of the above recording method.

FIG. 14 is a view showing a timing chart of a method for BCA recordingof medium identification information in a conventional example.

FIG. 15(a) is a block diagram showing an example of a modulation part ina recording device of the present invention; and

FIG. 15(b) is a block diagram showing an example of a demodulation partin a reproduction device of the present invention.

FIG. 16(a) is a structural view of data for BCA, where n=12 and 188bytes in an example of the present invention; and

FIG. 16(b) is a structural view of data for BCA, where n=1 and 12 bytesin an example of the present invention.

FIG. 17(a) is a structural view of data for BCA, where n=1 and 12 bytesin an example of the present invention; and

FIG. 17(b) is a structural view of virtual data created by adding 0 foran ECC operation for BCA, where n=1 and 12 bytes in an example of thepresent invention.

FIG. 18(a) is a structural view of data showing an example ofsynchronous codes of BCA of the present invention; and

FIG. 18(b) is a structural view of data showing a fixed synchronouspattern of BCA in an example of the present invention.

FIG. 19 is a wave form view showing a modulation signal in the case of aROM type disc in an example of the present invention.

FIG. 20 is a wave form view showing a modulation signal in the case of aRAM type disc in an example of the present invention.

FIG. 21 is a top view showing an example of the position of BCA on adisc of the present invention.

FIG. 22 is a process diagram showing an example of a process for forminga disc and recording BCA of the present invention.

FIG. 23 is a block diagram of a recording/reproduction device used forencryption and decryption of contents using an example of BCA of thepresent invention.

FIG. 24 is a flow chart showing a process for decrypting and reproducingthe contents in an example of the recording/reproduction device of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The optical recording medium of the present invention has theconfiguration in which information layers for recording informationsignals are provided in both the main information area and thesubsidiary information area, and subsidiary information to be recordedin the information layer of the subsidiary area is recorded withoutchanging the shape of the information layer. When a pattern of mediumidentification information such as a BCA pattern is formed, theinformation layer particularly in the boundary portion of the BCApattern causes unrecoverable defects such as separation or holes, anddue to these defects, the information layer of the main information areaalso becomes incapable of recording. This is a critical problem for arecording type optical recording medium, but this problem can be solvedby the configuration of the present invention described above. Theinformation layer of the subsidiary information area that recordssubsidiary information without changing its shape can be made of, forexample, optically active material such as pigment, magnetic materials,or phase change materials. According to the kind of the optically activematerial, for example, the recording may be performed by suitablyselecting the energy intensity etc. of a light source and/or a heatsource such as a laser beam. The shape change of the information layerreferred to in the present invention does not include, for example,ultra-micro changes such as the shape change of the information layeraccompanied with an atomic arrangement change between crystal andcrystal or between amorphousness and crystal, the shape change of theinformation layer accompanied with the chemical change of a materialcontained in the information layer, and the like.

The information layer of the main information area may be configured toinclude a phase change type material, for example, so that the phasestate of the medium identification information to be recorded in theinformation layer of the subsidiary information area and the phase stateof the information layer of the main information area can be changedindependently to control the phase state of the information layer in therespective areas. Alternatively, the portion for recording the mediumidentification information can be recorded with a phase that isdifferent from the phase state of the information layer of the maininformation area.

A main constituent material of the information layer in the maininformation area and a main constituent material of the informationlayer in the subsidiary information area may be configured to be thesame, so that the optical recording medium can be produced withoutchanging the material constitution for the information layer of thesubsidiary information area and the information layer of the maininformation area, so that the optical recording medium can be providedat a low price.

Furthermore, it may be configured such that, after the step of recordingmedium identification information is conducted, the step of recording aninformation signal with a modulation method that is different from alight beam modulation method used for the recording step of the mediumidentification information is conducted. Accordingly, the part where themedium identification information is recorded can be distinguishedeasily from the part where the information signal is to be recorded oris already recorded with a recording/reproduction device. In addition,the medium information in the part of the medium information signal canbe recognized precisely.

Furthermore, it is preferable to configure the method such that, afterthe step of recording the medium identification information and the stepof converting the phase are conducted, the step of recording theinformation signal in the information layer of the main information areais conducted, since, in the case where the information layer includes amagneto-optical recording material or a phase change recording material,the information signal can be recorded, reproduced and/or erased in theinformation layer of the main information area. Moreover, the step ofrecording the medium identification information and the step ofconverting the phase may be conducted at the same time, as will bedescribed later. Alternatively, these two steps can be treated as twoseparate steps and the order of the above steps can be selected, ifnecessary, for example, to conduct the step of recording the mediumidentification information after the step of converting the phase isconducted, or vice versa.

It may be configured such that a power of a light beam with which themedium identification information is recorded to the information layeris reduced to be lower than a power of a light beam to be emitted to theinformation layer other than the medium identification information part,for example, when the information layer includes a material that changesits phase between amorphousness and crystal, the medium identificationinformation can be recorded in the information layer in the state inwhich the film is formed (occupied mainly by the amorphous state), andthe phase can be converted to the crystal state except for the part ofthe medium identification information. Thus, the medium identificationinformation can be recorded with the use of an ordinary initialcrystallization device.

Furthermore, when the medium identification information is recorded byemitting a light beam to the information layer, the light beam may bescanned such that a part of a spot of the light beam is overlapped byanother spot in a main scanning direction of a circumferential directionof the spot and in a subsidiary scanning direction of a radial directionof the spot. For this purpose, the spot of the light beam having anarrower width than that of the medium identification signal in thecircumferential direction and a shorter length than that of the mediumidentification signal in the radial direction may be used. In this way,the spot can be scanned so as to overlap in the main scanning directionand in the subsidiary scanning direction.

In particular, by appropriately controlling the relative travellingspeed of the spot with the optical disc in the main scanning direction,the information layer in the part of the medium identificationinformation can remain unevenly distributed in the molten state, so thatit is possible also to pit the information layer as the mediumidentification information part formed in the reflective layer of thereproduction-only type optical recording medium. In this pitted part ofthe medium identification information, the information layer is unevenlydistributed in the liquid state. Therefore, compared with the method forforming pits by emitting a light beam having the size of the part of themedium identification information, the problems such as the occurrenceof particle etc. of the material contained in the information layerand/or the laminated film, or the separation of the information layerand/or the laminated film due to the impact caused by the evaporation orthe like can be solved. Moreover, since the width of the spot of thelight beam to be emitted to the part of the medium identificationinformation in the main scanning direction and the width thereof in thesubsidiary scanning direction, the power of the light beam and/or therelative speed between the light beam and the optical disc are dependentupon the material of the information layer in the optical disc and/orthe constitution or the material of the laminated film around theinformation layer, these elements are selected suitably for use.Furthermore, the preferable configuration of forming the part of themedium identification information to be pitted is effective, forexample, in preventing a user from tampering with the mediumidentification information. In this case, however, the shape of theinformation layer in the part of the medium identification informationnaturally is changed from the shape of other information layers.

In addition, the optical recording medium may be configured such that anamount of uneven distribution of the information layer in the subsidiaryinformation area is larger in a vicinity of an end side of a back partin a rotation direction of the subsidiary information than in a vicinityof an end side of a front part of the subsidiary information in therotation direction of the optical recording medium. Accordingly, it ispossible to pit the part of the medium identification information, andthe same optical characteristics as the medium identificationinformation of a reproduction-only type recording medium can beobtained.

In the present invention, it is preferable that the optical recordingmedium is a disc-shaped medium, and the subsidiary information area islocated along an inner peripheral surface of the lead-in area of thedisc-shaped medium. This location is most suitable for recording mediumidentification information.

Furthermore, in the present invention, it is preferable that thesubsidiary information area of a disc with a diameter of about 120 mm ispresent in the range between 22.3 mm and 23.5 mm from the center of thedisc, so that the optical pick-up is not structurally limited by themotor and the actuator, the movable range of the optical pick-up isincluded, and the main information is not affected thereby. The abovelocation is most suitable for recording medium identificationinformation as mentioned above.

Moreover, it is preferable that the subsidiary information is recordedwith an additional area (Burst Cutting Area) overwritten in thesubsidiary information area such that either an amorphous state is toremain in the stripe form or a crystal state is to remain in the stripeform. When the amorphous state is to remain in the stripe form in thesubsidiary information area, it is preferable that the phase of the maininformation area is changed continuously to the crystal state forinitialization. The case of allowing the crystal state to remain in thestripe form in the subsidiary information area is convenient when arecording film that does not need to be initialized (as-depo) is usedfor the main information area. The as-depo film is crystallized from thebeginning. However, by emitting the laser beam to such a degree that therecording film is not broken but has momentarily a high temperature, theas-depo film can be converted into an amorphous state.

In the above configuration, as for the recording film that isinitialized by changing the phase of the main information area to thecrystal state, chalcogenide based on Te or Se, for example, GeSbTe andGeTe can be used. Furthermore, the recording film which does not need tobe initialized (as-depo) can be formed, for example, by slowlydepositing GeSbTe of above chalcogenide by using the vapor phase thinfilm deposition such as the vacuum evaporation method.

In the above configuration, it is preferable that a phase changesbetween an amorphous state and a crystal state, and that thereflectivity in a crystal state is at least 10% higher than thereflectivity in an amorphous state. If a difference of 10% existsbetween the reflectivity, the recorded information can be distinguishedsurely.

Furthermore, it is preferable that the optical recording medium has adisc-shaped form, and when the medium identification information isrecorded by emitting a light beam to the information layer, the lightbeam is scanned such that a part of a spot of the light beam isoverlapped by another spot in a main scanning direction of acircumferential direction of the spot and in a subsidiary scanningdirection of a radial direction of the spot, and that the overlappedpart is determined to be the recorded information. According to thismethod, BCA signals can be formed without any break in the radialdirection, and the recorded BCA signals can be reproduced by using thelight beam that reproduces the main information.

Hereinafter, the present invention will be described by way ofembodiments with reference to drawings. The following embodiments aredescribed by using as the optical recording medium a rewritable typephase change optical disc in which the phase changes reversibly betweenamorphousness and crystal. However, the optical recording mediumapplicable to the present invention is not limited to the rewritabletype phase change optical disc. For example, so-called magneto-opticmaterials such as alloys of rare earth element and transition metal andso-called recordable information layer materials such as pigmentmaterials, i.e. cyanine dye, phthalocyanine dye etc. can be appliedthereto. Furthermore, the phase change type material changes its phasebetween amorphousness and crystal or between crystal and crystal. Sincethis is a conventionally known material, the details thereof will beomitted herein. The material that changes its phase reversibly orirreversibly also can be used.

Embodiment 1

FIG. 1 is a block diagram showing an example of a device for recordingmedium identification information in an optical disc. It will beexplained with regard to BCA as the medium identification information.The recording device of FIG. 1 includes a spindle motor 2 for rotatingan optical disc 1, a rotation controller 3, an optical pick-up 4 forfocusing light beams generated from a light source such as a laser, alaser power controller 5 for driving the light source of the opticalpick-up 4, a BCA signal generator 6 for generating a BCA signal bymodulating subsidiary information to be recorded on the optical disc, awaveform setter 7 for reshaping the laser modulation waveform based onthe BCA signal, a focus controller 8 for focusing the light emitted fromthe optical pick-up 4 on the optical disc, a feed motor 9 for shiftingthe optical pick-up 4 and a feed motor controller 10, a positiondetector 11 for detecting the position of the optical pick-up 4, and anoperation control system 12 for controlling the laser power controller5, the rotation controller 3, the focus controller 8 and the feed motorcontroller 10 as a whole.

FIG. 2 is a cross-sectional structural view showing the main part of aphase change type optical disc in an example of an optical discapplicable to the present invention. As illustrated in FIG. 2, arecording film 26 including a dielectric layer 22, a recording layer 23(a so-called information layer), a dielectric layer 24 and a reflectivelayer 25 is applied onto one side of the principal plane of atransparent substrate 21. An ultraviolet curable resin or the like isapplied thereto as a resin protection film 27 in contact with therecording film 26. A phase change type recording layer is provided asthe recording layer 23 in which information can be recorded by usingoptical means to change the phase state of the recording layer. Twopieces of this substrate as one pair are glued together via an adhesivelayer 28 to be finished as a single optical disc. Moreover, an opticaldisc configured symmetrically via the adhesive layer 28 naturally can beapplied as well. The recording film 26 in the embodiment shown in FIG. 2was formed by the sputtering method with the use of Zn—SiO₂ (thickness:120 nm) as the dielectric layer 22, GeTeSb (thickness: 20 nm) as therecording layer 23, Zn—SiO₂ (thickness: 30 nm) as the dielectric layer24, and an Al alloy (thickness: 90 nm) as the reflective layer 25.

FIG. 3 is the top view of the phase change type optical disc shown inFIG. 2. As illustrated in FIG. 3, there are a main information recordingarea 31 and a subsidiary information recording area 32 on the opticaldisc 1. The main information refers to the information that is recorded,reproduced, or erased by a user with an optical recording/reproductiondevice, whereas the subsidiary information refers to ID (identificationinformation), an encryption key, a decryption key or the like that isdifferent for each disc, which is recorded when the optical disc ismanufactured. Hereinafter, the embodiments of the present invention willbe explained on the basis of a BCA recording for recording thesubsidiary information. Furthermore, the subsidiary information areaincludes a pit part formed by pitting in which position information andthe like related to the main information is recorded besides theinformation described above. Generally, BCA is recorded in this areawhere pits are formed by partially overlapping with the recording layer.The subsidiary information recording area 32 is present in the rangebetween 22.3 mm and 23.5 mm from the center of the optical disc 1. Thisarea also is called a lead-in area. Furthermore, in the embodiment shownin FIG. 3, the subsidiary information recording area 32 was recorded byusing a laser with a wavelength of 810 nm, and this subsidiaryinformation recording area 32 was reproduced by using a laser with awavelength of 660 nm. As a result, the reflectivity in the part of thecrystal state was 16%, whereas the reflectivity in the part of theamorphous state was 2.5%.

FIG. 4 is a flow chart showing the process of recording BCA in a phasechange type optical disc of the present invention. The process ofrecording BCA will be explained with reference to FIG. 4. The process ofrecording BCA is divided largely into three sequences: a startingsequence 41, a BCA recording sequence 42, and an ending sequence 43.

First, the starting sequence 41 will be explained. In the step 41 a, thespindle motor 2 is driven by the rotation controller 3 according to theinstruction given from the operation control system 12, and the opticaldisc 1 is rotated at a constant angular velocity (CAV state). In thestep 41 b, the feed motor 9 controlled by the feed motor controller 10rotates screws 13 that support the optical pick-up 4, thereby shiftingthe optical pick-up 4 in the radial direction of the optical disc 1 tothe starting position of subsidiary information recording. In the step41 c, based on the instruction given from the operation control system12, the laser power controller 5 drives a high output laser 14 such as asemiconductor laser used as the light source. A light beam emitted fromthe laser 14 is directed through the optical system of the opticalpick-up 4 and a final objective lens 15 to the optical disc. At thistime, the power of light emitted from the laser 14 is of such a degreethat the recording layer 23 of the optical disc 1 is not crystallized.In the step 41 d, the focus controlling is performed in which the lightbeam emitted from the laser 14 is focused on the recording film of theoptical disc 1. The light reflected from the optical disc 1 is detectedby an optical detector 16 and output from the optical director 16 as anelectric signal. This output signal is amplified by a preamplifier 17and input to the focus controller 8. Based on the input signal from theoptical detector, the focus controller 8 drives a voice coil 18 of theoptical pick-up 4 so as to shift the objective lens 15 slightly in thevertical direction of the optical disc and thereby controls the lightbeam to be focused on the recording film. In the step 41 e, the positiondetector 11 detects the position of the optical pick-up and transmitsthe position information to the operation control system 12. In the step41 f, based on the obtained position information, the operation controlsystem 12 detects that the position of the light beam is located in thestarting position of subsidiary information recording. Then, theoperation control system 12 outputs a subsidiary information recordingsignal to the waveform setter 7 and also starts the BCA recordingsequence 42. When the position of the light beam is not located in thestarting position of subsidiary information recording, the operationcontrol system 12 sends a signal to the feed motor controller 10, andthe feed motor controller 10 drives the feed motor 9 based on thissignal so as to shift the optical pick-up 4 slightly to the startingposition of subsidiary information recording. Thereafter, the operationreturns to the step 41 e.

Next, the BCA recording sequence 42 will be explained. In the step 42 a,as shown in FIG. 5 (1), the recording data (subsidiary information) suchas identification information to be recorded on the optical disc 1 isencoded so as to generate a BCA pattern (recording signal) asillustrated in FIG. 5 (2). In the step 42 b, the waveform setter 7generates a laser modulation waveform based on the BCA pattern. Based onthe BCA signal sent from the BCA signal generator 6 and the rotationalfrequency from the operation control system 12, the waveform setter 7forms the laser modulation waveform, which is a reversed waveform of theBCA signal as shown in FIG. 5 (3), by taking one rotation pulse signalfrom the rotation controller 3 as the timing. Furthermore, the waveformsetter 7 outputs the laser modulation waveform in the case where asubsidiary information recording signal is input from the operationcontrol system 12, and in the case where a subsidiary informationrecording signal is not input, a bias output is performed, which has alower power than that of the subsidiary information recording signal,such as a reproduction output or the like. While the optical disc 1rotates one cycle, the step 42 c and the step 42 d are performed at thesame time. In the step 42 c, BCA is recorded on the optical disc 1. Thelaser power controller 5 drives the laser based on the laser power valueinstructed by the operation control system 12 and the laser modulationwaveform from the waveform setter 7, and the laser beam is output asillustrated in FIG. 5 (4). With regard to the light power of FIG. 5 (4),the power 51 a is a laser power capable of providing the necessaryenergy for crystallizing the recording film 26 of the optical disc 1,and the power 51 b is power of such a degree that the recording layer 26of the optical disc 1 is not crystallized (for example, reproductionpower).

Next, with reference to FIG. 6, the step of recording BCA onto theoptical disc 1 by the light power shown in FIG. 5(4) will be explained.A light beam 61 is focused on the recording film 26 of the optical disc1 and is moved relatively on the optical disc 1 by rotating the opticaldisc 1 (the travelling direction of the optical disc 1 is indicated withthe arrow in FIG. 6). Based on the laser modulation waveform generatedby the waveform setter 7, the laser power controller 5 modulates theoutput power of the laser beam. When the light power is 51 a, therecording film 26 is crystallized. On the other hand, when the lightpower is 51 b, the recording film 26 remains in the state in which thefilm was formed (mainly in the amorphous state), so that the recordingfilm 26 is crystallized intermittently for recording BCA.

In the step 42 d, while the optical disc 1 rotates one cycle, theoptical pick-up 4 is shifted in the radial direction of the optical disc1. By referring to FIG. 7, the process of recording a BCA pattern whileshifting the optical pick-up will be explained. A focus spot 71 focusedon the recording film 26 of the optical disc 1 has an oblong shape tothe radial direction of the optical disc 1. A moving amount 72 of theoptical pick-up 4 per one cycle of the spindle motor is equal to orsmaller than the length 71 a of the focus spot 71 in the radialdirection. According to the instruction from the operation controlsystem 12, the feed motor controller 10 drives the feed motor 9 andshifts the optical pick-up 4 so as to synchronize with the rotation ofthe spindle motor 2 at a constant speed. At the same time, as alreadydescribed in the step 42 c, the laser beam is modulated by taking onecycle pulse as a reference, so that a BCA pattern in the stripe form isformed in the subsidiary information recording area of the optical disc1 according to the principle shown in FIG. 6.

In the step 42 e, the position detector 11 detects the position of theoptical pick-up and transmits the position information to the operationcontrol system 12. In the step 42 f, based on the obtained positioninformation, the operation control system 12 detects that the positionof the light beam is located inside the subsidiary information recordingarea. Then, the operation control system 12 outputs a subsidiaryinformation recording signal to the waveform setter 7, and the operationreturns to the step 42 b. When the position of the light beam goesbeyond the subsidiary information recording area, the operation moves onto the ending sequence 43.

Next, the ending sequence 43 will be explained. In the step 43 a, theoperation control system 12 sends a signal to the laser power controller5 to return the light power to reproduction power. In the step 43 b, theoperation control system 12 sends a signal to the focus controller 8 tostop the focus controlling. In the step 43 c, the operation controlsystem 12 sends a signal to the laser power controller 5 to reduce thelaser power to zero.

According to the method described above, BCA can be recorded by allowingthe amorphous state in the stripe form to remain in the subsidiaryinformation recording area of the optical disc 1 shown in FIG. 3.

FIG. 5 shows a case in which the phase change type optical disc with BCArecorded according to the method described above is reproduced by usingan ordinary optical information recording/reproduction device. In thiscase, the BCA pattern recorded on the optical disc is formed in thestripe form as in FIG. 5 (5). When this stripe is reproduced with anoptical head of an ordinary optical information recording/reproductiondevice, it is reproduced as in FIG. 5 (6), since the part in theamorphous state has lower reflectivity than the crystal state. Thisreproduction signal is almost the same as the BCA reproduction signal ina conventional reproduction-only type optical recording mediumillustrated in FIG. 14 (4). By passing this reproduction signal througha low-pass filter, a signal such as FIG. 5 (7) can be obtained, whichthen is level-sliced to obtain the reproduction data such as FIG. 5 (8).

In this embodiment, the laser modulation waveform in the waveform setterwas generated by taking one cycle pulse signal from the spindle motor 2as the reference, but there is another method of setting the generationtiming of the intermittent pulse by providing the spindle motor 2 with arotary encoder and taking the turning angle signal of the optical disc 1detected by this rotary encoder as the reference. According to thismethod, BCA recording position errors caused by the rotationalfluctuation of the spindle motor 2 or the like can be reduced, andfurthermore, the BCA recording can improve its position accuracy.

In this embodiment, the rotation of the optical disc 1 is explained bysetting the state at a constant angular velocity (CAV), but there isanother method of setting the rotation of the optical disc 1 at aconstant linear velocity (CLV) by providing the spindle motor 2 with arotary encoder and taking the turning angle signal of the optical disc 1detected by this rotary encoder as the reference. According to thismethod, the laser power for the crystallization of the recording filmcan be regulated to be of a constant intensity, therefore, there is alsono time difference of crystallization by the linear velocity change. Asa result, a stable crystal state can be obtained.

In this embodiment, the laser output for allowing the crystallization tobe intermittent is explained by using a rectangular waveform as in FIG.6, but there is another method of setting the laser power to be amulti-pulse waveform. According to this method, the heating value givento the disc surface by the laser beam can be controlled to an amountthat is necessary for crystallizing only the crystallization area.Furthermore, the crystallization area can be prevented from spreading bythe residual heat, so that an optimal state of BCA recording can beobtained.

Embodiment 2

FIG. 8 is a block diagram showing the configuration of a BCA recordingdevice of the present invention, which is capable of recording BCA in anoptical disc and also of initializing the optical disc continuously.This recording device is characterized in that the BCA recording and theinitialization of the optical disc 1 can be performed continuously byadding a BCA recording control system 81, an initialization controlsystem 82 and a switching device 83 for switching the respective controlsystem in accordance with the situation to the BCA recording deviceillustrated in FIG. 1. This switching device 83 of the BCA recording andthe initialization is operated according to the signal sent from theposition detector 11, in which the switching device allows the BCArecording control system to take the control of the system when theposition of the light beam is within the subsidiary informationrecording area, whereas the switching device allows the initializationcontrol system to take the control of the system when the position ofthe light beam goes beyond the subsidiary information recording area.

With reference to the flow charts of FIG. 9 and FIG. 10, the actualoperation of this device will be explained below in an example in whichthe initialization is performed in the CLV state after the BCA recordingis performed in the CAV state. The process for this device is dividedlargely into four sequences: a starting sequence 41, a BCA recordingsequence 42, an initialization sequence 91, and an ending sequence 43.In the present embodiment, the starting position of subsidiaryinformation recording is determined to be a radial position 34 a in FIG.3, and the ending position of subsidiary information recording isdetermined to be a radial position 34 b in FIG. 3. In addition, thestarting position of initialization is determined to be the radialposition 34 b in FIG. 3, and the ending position of initialization isdetermined to be a radial position 34 c in FIG. 3.

First, the starting sequence 41 will be explained. In the step 41 a, thespindle motor 2 is driven by the rotation controller 3 according to theinstruction given from the operation control system 12, and the opticaldisc 1 is rotated at a constant angular velocity (CAV state). In thestep 41 b, the feed motor 9 rotates the screws 13 that support theoptical pick-up 4, thereby shifting the optical pick-up 4 in the radialdirection of the optical disc 1 to the starting position of subsidiaryinformation recording. In the step 41 c, based on the instruction givenfrom the operation control system 12, the laser power controller 5drives the laser 14. A light beam emitted from the laser 14 is directedthrough the optical system of the optical pick-up 4 and the finalobjective lens 15 to the optical disc. At this time, the power of lightemitted from the laser 14 is of such a degree that the recording layer23 of the optical disc 1 is not crystallized. In the step 41 d, thefocus controlling is performed in which the light beam emitted from thelaser 14 is focused on the recording film of the optical disc 1. In thestep 41 e, the position detector 11 detects the position of the opticalpick-up and transmits the position information to the operation controlsystem 12. In the step 41 f, based on the obtained position information,the operation control system 12 detects that the position of the lightbeam is located in the starting position of subsidiary informationrecording. Then, the operation control system 12 outputs a subsidiaryinformation recording signal to the waveform setter 7 and also startsthe BCA recording sequence 42. When the position of the light beam isnot located in the starting position of subsidiary informationrecording, the operation control system 12 sends a signal to the feedmotor controller 10, and the feed motor controller 10 drives the feedmotor 9 based on this signal so as to shift the optical pick-up 4slightly to the starting position of subsidiary information recording.Thereafter, the operation returns to the step 41 e.

Next, the BCA recording sequence 42 will be explained. In the step 42 a,the recording data (subsidiary information) to be recorded on theoptical disc 1 such as identification information is encoded so as togenerate a BCA pattern (recording signal). In the step 42 b, thewaveform setter 7 generates a laser modulation waveform based on the BCApattern. On the basis of the BCA signal sent from the BCA signalgenerator 6 and also of the rotational frequency from the operationcontrol system 12, the waveform setter 7 forms the laser modulationwaveform, which is a reversed waveform of the BCA signal, by taking onerotation pulse signal from the rotation controller 3 as the timing.Furthermore, the waveform setter 7 outputs the laser modulation waveformin the case where a subsidiary information recording signal is inputfrom the operation control system 12, and in the case where a subsidiaryinformation recording signal is not input, a bias output is performed.While the optical disc 1 rotates one cycle, the step 42 c and the step42 d are performed at the same time.

In the step 42 c, BCA is recorded on the optical disc 1. The laser powercontroller 5 drives the laser based on the laser power value instructedby the operation control system 12 and the laser modulation waveformfrom the waveform setter 7, and the laser beam is output as illustratedin FIG. 5 (4). With regard to the light power in FIG. 5 (4), the power51 a is a laser power capable of providing the necessary energy forcrystallizing the recording film 26 of the optical disc 1, and the power51 b is power of such a degree that the recording layer 26 of theoptical disc 1 is not crystallized (for example, reproduction power). Asillustrated in FIG. 6, by emitting this modulated light beam to therecording film of the optical disc 1, the recording film 26 iscrystallized intermittently so as to record BCA.

In the step 42 d, while the optical disc 1 rotates one cycle, theoptical pick-up 4 is shifted for a predetermined amount in the radialdirection of the optical disc 1 at a constant speed, as illustrated inFIG. 7. By performing the step 42 c and the step 42 d at the same time,a BCA pattern in the stripe form is formed in the subsidiary informationrecording area of the optical disc 1.

In the step 42 e, the position detector 11 detects the position of theoptical pick-up and transmits the position information to the operationcontrol system 12. In the step 42 f, based on the obtained positioninformation, the operation control system 12 detects that the positionof the light beam is located inside the subsidiary information recordingarea. Then, the operation control system 12 outputs a subsidiaryinformation recording signal to the waveform setter 7, and the operationreturns to the step 42 b. When the position of the light beam goesbeyond the subsidiary information recording area, the operation moves onto the initialization sequence 91 shown in FIG. 10.

Next, the initialization sequence 91 will be explained. When theposition of the light beam moves out from the subsidiary informationrecording area to the initialization area, the switching device 83allows the initialization control system to take control of the system.In the step 91 a, the operation control system 12 sends a signal to therotation controller to switch the rotational condition from the CAVstate to the CLV state. In the step 91 b, the operation control system12 sends a signal to the laser power controller 5, and the laser powercontroller 5 controls the laser power such that a constant powernecessary for the recording film 26 of the optical disc 1 to becrystallized is provided for a predetermined linear velocity. In thestep 91 c, while the optical disc 1 rotates one cycle, the feed motorcontroller 10 drives the feed motor 9 to shift the optical pick-up by apredetermined amount. In the step 91 d, the position detector 11 detectsthe position of the optical pick-up and transmits the positioninformation to the operation control system 12. Based on the obtainedposition information, the operation control system 12 detects that theposition of the light beam is located inside the initialization area,and the operation returns to the step 91 c. When the position of thelight beam goes beyond the initialization area, the operation moves onto the ending sequence 43.

Next, the ending sequence 43 will be explained. In the step 43 a, theoperation control system 12 sends a signal to the laser power controller5 to return the light power to reproduction power. In the step 43 b, theoperation control system 12 sends a signal to the focus controller 8 tostop the focus control. In the step 43 c, the operation control system12 sends a signal to the laser power controller 5 to reduce the laserpower to zero.

According to the operation described above, after BCA is recorded in thesubsidiary information recording area on the optical disc 1 by changingthe phase state of the recording film 26, the optical disc 1 can beinitialized continuously, so that the manufacturing process can besimplified.

Furthermore, although Embodiment 2 is described by referring to the casein which the initialization is performed in the CLV state after the BCArecording is performed in the CAV state, it is also possible to recordBCA after the initialization process. Moreover, it is also possible toperform the BCA recording and the initialization continuously in the CAVstate alone by controlling the laser power intensity in conformity withthe linear velocity. In addition, the BCA recording and theinitialization can be performed continuously in the CLV state alone byattaching a rotary encoder to the spindle motor and generating a lasermodulation signal during the BCA recording with reference to the turningangle signal of the optical disc 1 to be detected by the rotary encoder.

Embodiment 3

With the use of the device shown in FIG. 8, a method for recording a BCApattern by providing a through hole that penetrates a recording layerand/or a recording film or a depression hole (hereinafter referred to asa hole) will be explained. According to the present invention, comparedwith the conventional method for recording a BCA pattern by using onelaser emission for one BCA pattern, a light beam is emitted for severaltimes to form a light spot that is sufficiently smaller than the BCApattern, so that the thermal influence and the thermal damage to therecording film and to its peripheral portion can be reduced, therebyforming excellent holes (BCA patterns). Furthermore, as illustrated inFIG. 11, this method can be accomplished by increasing the power of thelaser beam to such a power 111 a that the film starts to break in thepart of BCA recording. According to this method, it is possible toinitialize the optical disc and also to record BCA by making holes inthe recording film as in the conventional method.

With reference to the flow charts of FIG. 12 and FIG. 13, the actualoperation of this device will be explained below in an example in whichthe initialization is performed in the CLV state after the BCA recordingwas performed in the CAV state. The process for this device is dividedlargely into four sequences: a starting sequence 41, a BCA recordingsequence 121, an initialization sequence 131, and an ending sequence 43.Moreover, the starting position of subsidiary information recording isdetermined to be a radial position 34 a in FIG. 3, and the endingposition of subsidiary information recording is determined to be aradial position 34 b in FIG. 3. In addition, the starting position ofinitialization is determined to be a radial position 34 a in FIG. 3, andthe ending position of initialization is determined to be a radialposition 34 c in FIG. 3.

First, the starting sequence 41 will be explained. In the step 41 a, thespindle motor 2 is driven by the rotation controller 3 according to theinstruction given from the operation control system 12, and the opticaldisc 1 is rotated at a constant angular velocity (CAV state). In thestep 41 b, the feed motor 9 rotates the screws 13 that support theoptical pick-up 4, thereby shifting the optical pick-up 4 in the radialdirection of the optical disc 1 to the starting position of subsidiaryinformation recording. In the step 41 c, based on the instruction givenfrom the operation control system 12, the laser power controller 5drives the laser 14. A light beam emitted from the laser 14 is directedthrough the optical system of the optical pick-up 4 and the finalobjective lens 15 to the optical disc. At this time, the power of lightemitted from the laser 14 is of such a degree that the recording layer23 of the optical disc 1 is not crystallized. In the step 41 d, thefocus controlling is performed in which the light beam emitted from thelaser 14 is focused on the recording film of the optical disc 1. In thestep 41 e, the position detector 11 detects the position of the opticalpick-up and transmits the position information to the operation controlsystem 12. In the step 41 f, based on the obtained position information,the operation control system 12 detects that the position of the lightbeam is located in the starting position of subsidiary informationrecording. Then, the operation control system 12 outputs a subsidiaryinformation recording signal to the waveform setter 7 and also startsthe BCA recording sequence 42. When the position of the light beam isnot located in the starting position of subsidiary informationrecording, the operation control system 12 sends a signal to the feedmotor controller 10, and the feed motor controller 10 drives the feedmotor 9 based on this signal so as to shift the optical pick-up 4slightly to the starting position of subsidiary information recording.Thereafter, the operation returns to the step 41 e.

Next, the BCA recording sequence 121 will be explained. In the step 121a, the recording data (subsidiary information) to be recorded on theoptical disc 1 such as identification information is encoded to generatea BCA pattern (recording signal). In the step 121 b, the waveform setter7 generates a laser modulation waveform based on the BCA pattern. On thebasis of the BCA signal sent from the BCA signal generator 6 and also ofthe rotational frequency from the operation control system 12, thewaveform setter 7 forms the laser modulation waveform by taking onerotation pulse signal from the rotation controller 3 as the timing.Furthermore, the waveform setter 7 outputs a laser modulation waveformin the case where a subsidiary information recording signal is inputfrom the operation control system 12, and in the case where a subsidiaryinformation recording signal is not input, a bias output is performed.While the optical disc 1 rotates one cycle, the step 121 c and the step121 d are performed at the same time. In the step 121 c, BCA is recordedon the optical disc 1. The laser power controller 5 drives the laserbased on the laser power value instructed by the operation controlsystem 12 and the laser modulation waveform from the waveform setter 7,and the laser beam is output as illustrated in FIG. 11 (1). With regardto the light power in FIG. 11 (1), the power 111 a is a laser powercapable of providing the necessary energy for breaking the recordingfilm 26 of the optical disc 1 and making holes therein, and the power111 b is power of such a degree that the recording layer 26 of theoptical disc 1 is not crystallized (for example, reproduction power). Byemitting this modulated light beam to the recording film of the opticaldisc 1, holes are formed intermittently in the recording layer and/orthe recording film so as to record BCA.

In the step 121 d, while the optical disc 1 rotates one cycle, theoptical pick-up 4 is shifted for a predetermined amount in the radialdirection of the optical disc 1 at a constant speed. By performing thestep 121 c and the step 121 d at the same time, a BCA pattern in thestripe form is formed in the subsidiary information recording area ofthe optical disc 1. In the step 121 e, the position detector 11 detectsthe position of the optical pick-up and transmits the positioninformation to the operation control system 12. In the step 121 f, basedon the obtained position information, the operation control system 12detects that the position of the light beam is located inside thesubsidiary information recording area. Then, the operation controlsystem 12 outputs a subsidiary information recording signal to thewaveform setter 7, and the operation returns to the step 121 b. When theposition of the light beam goes beyond the subsidiary informationrecording area, the operation moves on to the initialization sequence131 shown in FIG. 13.

Next, the initialization sequence 131 will be explained. When theposition of the light beam moves out from the subsidiary informationrecording area, the switching device 83 allows the initializationcontrol system to take the control of the system. In the step 131 a, theoperation control system 12 sends a signal to the laser power controller5 and returns the laser power to reproduction power. In the step 131 b,the optical pick-up 4 is shifted in the radial direction of the opticaldisc 1 to the starting position of initialization.

In the step 131 c, the operation control system 12 sends a signal to therotation controller to switch the rotational condition from the CAVstate to the CLV state. In the step 131 d, the operation control system12 sends a signal to the laser power controller 5, and the laser powercontroller 5 controls the laser power such that a constant powernecessary for the recording film 26 of the optical disc 1 to becrystallized is provided to a predetermined linear velocity. In the step131 e, while the optical disc 1 rotates one cycle, the feed motorcontroller 10 drives the feed motor 9 to shift the optical pick-up by apredetermined amount. In the step 131 the position detector 11 detectsthe position of the optical pick-up and transmits the positioninformation to the operation control system 12. Based on the obtainedposition information, the operation control system 12 detects that theposition of the light beam is located inside the initialization area,and the operation returns to the step 131 e. When the position of thelight beam goes beyond the initialization area, the operation moves onto the ending sequence 43.

Next, the ending sequence 43 will be explained. In the step 43 a, theoperation control system 12 sends a signal to the laser power controller5 to return the light power to reproduction power. In the step 43 b, theoperation control system 12 sends a signal to the focus controller 8 tostop the focus control. In the step 43 c, the operation control system12 sends a signal to the laser power controller 5 to reduce the laserpower to zero.

According to the operation described above, after BCA is recorded in thesubsidiary information recording area on the optical disc 1 by makingholes in the recording film 26, the optical disc 1 can be initializedsuccessively, so that the manufacturing process can be simplified.

In this embodiment, with respect to the BCA recording waveform, thelaser power is determined to be the reproduction power other than forthe part of BCA recording as in FIG. 11 (1). However, there is anothermethod of determining the starting position of initialization to be theradial position 34 b of FIG. 3 and determining the laser power to be theinitialization power besides the part of BCA recording as in FIG. 11(3). According to this method, the initialization area is reduced, sothat the processing capability can be improved.

Furthermore, although Embodiment 3 is described by referring to the casein which the initialization is performed in the CLV state after the BCArecording is performed in the CAV state, it is also possible to recordBCA after the initialization process. Moreover, it is also possible toperform the BCA recording and the initialization continuously in the CAVstate alone by controlling the laser power intensity in conformity withthe linear velocity. In addition, the BCA recording and theinitialization also can be performed continuously in the CLV state aloneby attaching a rotary encoder to the spindle motor and generating alaser modulation signal during the BCA recording with reference to theturning angle signal of the optical disc 1 to be detected by the rotaryencoder.

The configuration of making holes in the recording layer and/or therecording film as described in Embodiment 3 above is effective inpreventing a user from tampering with the medium identificationinformation without permission. In addition, the effect of forming thesame medium identification information as the reproduction-only typeoptical recording medium can be obtained.

Moreover, although Embodiment 3 is described by referring to the case inwhich holes are provided in the recording layer and/or the recordingfilm for recording medium identification information, the presentrecording method also is applicable to the recording layer and/orrecording film in the main information area. This method, when appliedto the main information area, can prevent a part of information frombeing tampered even as a rewritable type optical disc, so that therecording method capable of both uses as a rewritable type and anadditional type can be achieved.

Furthermore, when holes are provided in the recording layer and/or therecording film, for example, by using the configuration described inEmbodiment 3 of optimizing the linear velocity of the optical disc toliquefy the recording layer and/or the recording film to be distributedunevenly due to the surface tension, as for the hole part, the materialof the recording layer and/or the recording film is distributed unevenlyin each hole in the vicinity of the front end side (i.e. side of thestarting point of recording) in the rotational direction (i.e. in thetravelling direction) and in the vicinity of the back end side (i.e.side of the ending point of recording). In addition, the amount ofuneven distribution in the vicinity of the back end side becomes largerthan the amount of uneven distribution in the vicinity of the front endside so that the hole part is formed asymmetrically; still since theoptical change due to the hole part is larger, the change due to theasymmetrical part can be absorbed sufficiently. Moreover, since thematerial of the hole part is distributed unevenly due to the surfacetension of the material in the molten state, the impact forceaccompanied by the vaporization of the material or the like can besuppressed, and the separation of the recording layer and/or therecording film and the like also does not occur.

The configuration of the optical disc applied to the present inventionsis exactly the same with the exception of a reflective layer. However,particularly in the case where the optical disc that is configured so asto be provided with through holes has a reflective layer as inEmbodiment 3, the holes preferably are formed to penetrate to thereflective layer. In the case of the medium identification informationrecorded as holes penetrating to the reflective layer, exactly the samemedium identification information as the reproduction-only type opticalrecording medium can be obtained.

In Embodiments 1 to 3 above, the basic methods for recording BCA aredescribed. In Embodiment 4 below, a modulation method at the time ofrecording and a demodulation method at the time of reproducing will beexplained in detail. Furthermore, Embodiment 5 is an example of applyingthis BCA, in which a method for preventing security from deterioratingdue to tampering will be explained, which is assumed to happen in thesystem of BCA that also is used for initialization.

Embodiment 4

With reference to FIG. 15(a), a modulation method for data will beexplained in detail. First, as for data to be recorded, a Reed-Solomonsystem error correction code (ECC) 717 is appended to data 716 in an ECCappending part 715. FIG. 16(a) shows a data configuration in which aReed-Solomon code is calculated for each of the data 716 of 188 bytesand a 16-bytes ECC 717 is appended. FIG. 16(b) shows a dataconfiguration in the case of recording the data 716 a of 12 bytes. Theamount of data in the ECC 717 a is 16 bytes, so that the data size isthe same with that of the ECC part having the data of 188 bytes.

The ECC calculation of the present invention operates such that, whenthe data has 12 bytes, the data 716 a of 12 bytes are not calculated asin the usual manner, but instead, as illustrated in FIG. 17(b), avirtual data configuration 716 b of 188 bytes is generated in which 0 isinserted in 166 bytes starting from the last row of RS₁ through thenon-existent RS₂ up to the third row of RS_(n). In this way, thecalculation for error correction is carried out to generate the ECC 717b.

In the case of calculating the error correction of BCA with a smallcapacity microcomputer of 8 bits or 16 bits used for a DVD drivecontrol, according to the conventional system of performing the ECCcalculation in the total of 12 different kinds including 12 bytes, 28bytes, and those between 44 bytes and 188 bytes, greater programcapacity and greater memory space are required for each calculationprogram, so that the program capacity and the memory space may not besufficient. The present invention is effective in performing the ECCprocess with the use of a small capacity microcomputer on which anexisting drive is mounted.

Synchronous Code

Next, a synchronous code will be explained. FIG. 18(a) shows synchronousbits 719 a to 719 z. As illustrated in FIG. 18(b), the fixed pattern ofthe synchronous signal has an interval of 4T, so that it is easier todistinguish 3T of data and the synchronous pattern.

PE-RZ Modulation

As for the data 716 in which the ECC codes are inserted, when BCA isrecorded in the recording type media that perform the same grouprecording as DVD-ROM such as DVD-R and DVD-RW, 1 and 0 in the data arereversed in a reverse code conversion part 721 of a PE-RZ modulationpart 720 so as to be distinguished from ROM discs, which then goesthrough a PE-RZ modulation in an RZ modulation part 722 and in a PEmodulation part 723. To explain by using a waveform view of FIG. 20, (1)shows input data; (1′) shows bit reversed data; (2) shows a RZmodulation; and (3) shows a PE-RZ modulation signal. The pulse width ofthis modulation signal is reduced to 50% or less in a pulse width halfvalue part 724, and a waveform like FIG. 20 (4) is obtained. In the caseof a phase change type disc such as DVD-RW, the phase of the waveform isreversed by a sign reversing part 725, and an the initialization beam ofa laser 726 is turned OFF only in the BCA modulation part as shown asthe light power in (5). As shown in FIG. 20 (6), the BCA pattern isrecorded and the recording film between BCA is crystallized andinitialized. In the present invention, the recording pulse width isreduced to less than half of the original PE-RZ modulation signal, sothat the stripe width of each slot is reduced to half as illustrated inFIG. 20 (6). Furthermore, since only one stripe is present in 2 slots,the part of BCA, i.e. the low reflective part has a total of ¼ in width,that is, only ¼ in the area ratio of the BCA area 728.

When the recording film is made of a phase change material, a brightsection, which is a not yet recorded part, has a low reflectivity ofaround 20%. If the signal with the recording pulse width of aconventional PE-RZ signal is used as it is, half the width becomes adark section, which is a recorded part, having the average reflectivityof around 10%, as shown in FIG. 20 (3). Since the average reflectivelight is reduced, the focusing is effected negatively. In the presentinvention, the pulse width of BCA is reduced to half the width by thepulse width half value part 724, so that the average reflectivity has atleast 75% of the reflectivity in the original BCA or in the part wherepits are not present. Also with the use of a phase change recordingfilm, the average reflectivity of at least 15% can be obtained in theBCA area. As a result, it is easier to focus, and the focusing is morestable.

Recording in DVD-R

Furthermore, when this recording device is used for recording in DVD-R,by generating a sign reverse control signal and sending it to the signreversing part 725, the polarity of the light power in FIG. 20 (5) isreversed. Thus, the reflectivity of the recording film of DVD-R isreduced in the part where the laser is emitted, so that BCA as in FIG.20 (6) is recorded. Since the function of reversing the polarity of thewaveform is present, it is not necessary to reverse the polarity forrecording in DVD-R, whereas the polarity is reversed for recording inDVD-RW. In this way, it is effective in recording BCA for both of themedia with only one device. Since FIG. 20 has the code reversing part721, the values 1 and 0 in the modulation data are reversed comparedwith ROM-type discs. For comparison, the modulation signal of a ROM-typedisc is illustrated in FIG. 19.

In FIG. 19 and FIG. 20, the input data (1) are the same. However, a codereversing signal is not transmitted in the case of ROM, so that the codereversing part 721 is not operated. Therefore, when the value is “0”,the PE-RZ signal is arranged in the slot on the left side as shown inFIG. 19 (3), and the BCA pattern also is formed on the left side asshown in FIG. 19(b). On the other hand, a code reversing signal istransmitted in the case of RAM-type media such as DVD-RW, DVD-R and thelike, so that when the value is “0”, the PE-RZ signal is arranged in theslot on the right side as shown in FIG. 20 (3), and the BCA pattern isformed on the right side as shown in (c). As a result, the BCA patternson the discs are different, so that the BCA of ROM and the BCA of RAMcan be distinguished. If an illegal company uses this RAM disc of DVD-RWor DVD-R to copy data of a ROM disc, since the BCA pattern is different,it is identified as not being a ROM disc. In this way, it is effectivein preventing an illegal use of discs.

In the present invention, by turning the code reversing part 721 OFF andturning the sign reversing part 725 OFF, BCA can be recorded in a ROMdisc as in FIG. 19. It is possible to record regular BCA with onerecording device by setting the code reversing part and the signreversing part ONION for DVD-RW, ON/OFF for DVD-R, and OFF/ON forDVD-RAM. By switching the two parts in this way, it is effective inrecording BCA for four different media of DVD-ROM, DVD-R, DVD-RW andDVD-RAM with the same recording device.

Arrangement of BCA

The arrangement of BCA is shown in FIG. 21. As for DVD-ROM and DVD-RAM,the BCA area 728 is located in the inner most periphery of the lead-inarea, from the position where the radius is 22.3 mm to the positionwhere the radius is 23.5 mm. In this area, an address 729 is recorded,and since the recording angle of a BCA bar-code has a minimum of 51degrees and a maximum of 316 degrees, an unrecorded portion exists in acertain angular range of the BCA area. The address can be read in thisopen area 730, so that the head of the reproduction device can recognizeits own position. In the outer peripheral portion of the BCA area, aguard band 731 of more than 50 μm is provided, and in the further outerperipheral portion, control data 732 indicating the physical propertiesof the disc are recorded by pits. In the control data 732, a BCAexistence identifier 712, a disc type identifier 711, a copy preventionidentifier 735 for indicating a copy prevention disc, and a media keyblock 736, i.e. a key group are recorded.

In the case of DVD-R or DVD-RW, a PCA area 737 of a trial writing areafor power adjustment is provided in the radial range between22.1(21.9)mm and 22.3(22.1)mm of the inner peripheral portion of BCA.Also, an RMA area 738 for recording the history of power control isprovided in the radial range between 22.3(22.1)mm and 22.6(22.4)mm, anda subsidiary guard band 739 of more than 50 μm is provided in the innerperipheral portion of BCA to avoid the interference between the RMA areaand the BCA area 728. Thus, the BCA area 728 always is present in theradial range between 22.8 mm and 23.5 mm, and more specifically, between22.77 mm and 23.45 mm. By reducing the width of the BCA area in theradial direction compared with ROM, both the PCA and the RMA cancoexist, and BCA can be used for DVD-R and DVD-RW. In this case, thesuccessive initialization starts at least from the inner peripheralportion and continues to the radius of 22.65 mm. Then, BCA is recordedby emitting the beam intermittently based on the PE-RZ modulationsignal. In the radius of 23.57 mm, the beam is switched completely tosuccessive emission, so that BCA can be recorded by initializing andalso without breaking the RMA.

Reproduction Method

With reference to FIG. 15(b), a method for reproducing BCA will beexplained. First, the control data 732 are accessed by the optical headand demodulated in a 8-16 demodulation part 738. The BCA identifier 712is read out from the demodulated control data, and the operation isstopped when a BCA identifier determination part 739 outputs “0”, i.e.non-existence. On the other hand, when it outputs “1”, i.e. existence,the disc type identifier 711 is read, and only when a disc typeidentifier determination part 740 indicates that this is a recordingtype disc such as DVD-R or DVD-RW, a code reversing signal 745 isgenerated to operate a code reversing part 744.

On the other hand, when the BCA data are reproduced, the optical head isshifted to the BCA area 728 illustrated in FIG. 21 so as to reproducethe BCA signal and to change it to a digital signal by a level slicer714. Then, a synchronous signal is taken out by a synchronous signalreproduction part 743, and only the BCA data 716 are demodulated by thePE-RZ demodulation part 742. When the code reversing signal 745mentioned above is turned ON, it is converted as shown in FIG. 20(1′)and FIG. 20(1) in the code reversing part 744, and the values 0 and 1are reversed. In the case of ROM discs, the code reversing signal 745 isnot generated, so that the code is not converted. In this way, theoriginal BCA data are reproduced normally. In the Reed-Solomon errorcorrection part 746, in the case where BCA has less than 188 bytes as inFIG. 17(b), 0 data are added to virtually create 188 bytes in order tocorrect errors by calculating ECC. Thus, the BCA signals are outputcorrectly.

Embodiment 5

Recording Method of a Disc ID FIG. 22 shows an exemplary manufacturingprocess for a RAM disc with BCA. First, with the use of a firstencryption key 802 such as a public key or a private key, an encryptionkey group 700 including a plurality of the first to the nth codes isencrypted by a cryptographic encoder 803 to generate a first code 805.This first code 805 is modulated by an 8-16 modulator 917 in themastering device, and this modulated signal is recorded by a laser as anuneven pit in a first recording area 919 located in the inner peripheralportion of an original board 800. Specifically, as illustrated in FIG.21, this modulated signal is recorded in the control data area 732together with the BCA identifier 711, the disc type identifier 712, andthe copy prevention identifier 735. This original board 800 is used tomold a disc-shaped transparent substrate 918 with a molding machine 808a. A recording film made of a phase change type recording material or apigment material is formed on one side of the transparent substrate 918by a recording film forming machine 808 b, thereby two pieces ofsingle-side discs 809 a, 809 b 0.6 mm thick are created. These discs areglued together by a bonding machine 808 c to create a complete disc. Ina second recording area 920 of the completed disc 809, by using a BCArecording device 807, a signal of information of a disc ID 921 or asecond encryption key 923 for the internet communication is modulated bya PE-RZ modulator 807 a in which the PE modulation and the RZ modulationare combined. This modulated signal is recorded by a laser 807 b to forma BCA pattern. In this way, a recording type disc with BCA 801 ismanufactured. When a phase change type recording material is used, byusing the initializer of the present invention as the BCA recordingdevice, the two processes of initializing and BCA recording can beintegrated into one process. To describe this process, the recordingfilm after being formed by the recording film forming machine 808 b iseither in an amorphous state or in an as-depo state, so that thereflectivity is as low as less than 10%. When the initializer is used,the laser beam is focused on a stripe-form beam spot that is long in theradial direction to form an image on the recording surface by asemicylindrical lens, and the disc is rotated. Along with the rotation,the beam is shifted to the outer peripheral portion, and when the beamis emitted continuously, the recording film changes from the amorphousstate having low reflectivity to the crystal state having highreflectivity. The disc is initialized continuously from the innerperiphery to the outer periphery. In this state, in the second recordingarea, by turning the laser beam OFF, which is signal 0, when the PE-RZsignal is in the “0 state”, and by turning the laser beam ON, which issignal 1, when the PE-RZ signal is in the “1 state”, the amorphous statewith low reflectivity remains in the area where the laser is turned OFF,whereas the condition changes to the crystal state with highreflectivity in the area where the laser beam is turned ON. As a result,bar-codes are formed on the circumference, and BCA is recorded. When thelaser beam moves on to the outer peripheral portion of BCA and reachesthe inner peripheral portion of the guard band 731 in FIG. 21, bychanging the laser from the emission state at intervals continuously tothe ON state according to the BCA signals, the entire recording filmthat is located further in the outer peripheral portion than the guardband 731 is crystallized, that is, initialized to the outermostperiphery.

In the case of DVD-RW, the inner peripheral portion of the BCA isprovided with the PCA area 737, the RMA area 738 and the guard band 739from the area of at least 22.1 mm, 21.9 mm in radius by taking thetolerance in consideration, to the area of 22.6 mm in radius, 22.4 mm inradius by taking the tolerance in consideration. Therefore, the laser isemitted continuously in the first inner peripheral portion and thenstarts to be emitted intermittently based on the BCA modulation signalsin the position between 22.65 mm and 22.77 mm in radius (between about22.6 and 22.8 mm) so as to record the BCA pattern in the BCA area 728.Then, the laser is switched from the intermittent emission to thesuccessive emission in the position between 23.45 mm and 23.55 mm inradius. Accordingly, BCA is not recorded in the guard band 731 of FIG.21, while the control data 732 in the outer peripheral portion of BCA aswell as the PCA area 737 and the RMA area 738 in the inner peripheralportion of BCA are initialized completely on the entire circumference.Therefore, this configuration is effective in reading data or addressesstably by the optical head in the PCA and RMA areas.

The disc used here is a bonded disc, and the BCA inserted in the disccannot be tampered with, which can be used for security purposes.Furthermore, a DVD-RAM drive and a DVD-RW drive that are commonlyavailable on the market have circular beam spots. Even if an illegaluser tries to tamper with the BCA part with the circular beam of thiscommercial drive or tries to erase BCA, the amorphous state remainsbetween the tracks, so that BCA cannot be erased completely. As aresult, commercial drives cannot be used for tampering with the BCAdata, and therefore, high security effects can be obtained as a consumerproduct. On the other hand, a disc that is exactly like a DVD-ROM may becopied by using a group recording type RAM disc such as a DVD-RW or aDVD-R. To prevent this from happening, as explained in FIG. 20, themodulation rule is reversed compared with a ROM disc only in the datapart of the PE-RZ modulation by the code polarity reversing part 820 b.Specifically, in the case of ROM, when the BCA data are “0,” and “1”,the modulated signals are respectively “01” for “10”, while themodulated signals are respectively reversed to “01”, “10” in the case ofRAM. Thus, the PE-RZ modulated signals in the ROM and the RAM aredifferent, so that the attempt to create a copy of a ROM disc with a RAMdisc can be distinguished and detected that it is illegal. As a result,the copy prevention can be achieved.

Application to Copyright Protection

With reference to FIG. 23, an example of applying thishard-to-tamper-with BCA to copyright protection will be explained.First, the encryption procedure with the use of BCA at the time whencontents are permitted to be copied only once to a RAM disc will beexplained. When an only once copy permission identifier is detected, aBCA area 920 of a RAM disc 856 is accessed, and the BCA data arereproduced by the PE-RZ demodulation in a BCA reproduction part 820, andthen an ID 857 peculiar to the disc is output. Furthermore, while thefirst to the n-th key, i.e. a plurality of key groups 700 are recordedin a second recording area 919 of the RAM disc 856, a key authorized foreach manufacturer's drive is selected by a key selection part 703, whichis decoded by a cryptographic decoder 708 so as to generate the “firstkey”. When this “first key” and the ID 857 peculiar to the disc arecalculated in an operation part 704 by the one-way function, the “secondkey” is generated. This key is peculiar to each RAM disc and alsodifferent for each disc. This “second key” is sent to a cryptographicpart 706 in an encryption part 859.

In the encryption part 859, a contents key 705 is generated by a randomnumber generator 709 in a contents key generation part 707. Thiscontents key is encrypted by using the “second key” described above inthe cryptographic part 706. This “encrypted contents key” is recorded bya recording circuit 862 in a recording area 702 of the disc 856.

On the other hand, contents 860 comprising picture signals such as movieor sound signals such as music are encrypted with the use of thecontents key 705 in the cryptographic encoder 861 and recorded by therecording circuit 862 in the recording area 702 of the RAM disc 856.

Next, the process of reproducing this contents signal will be explainedwith reference to a block diagram of FIG. 23 and a flow chart of FIG.24. First, a disc is inserted (step 714 a); a reproduction order of thecontents is received (step 714 b); a copy prevention identifier 735 inthe control data 732 of the disc is referred to for judging whether thisdisc is a copy prevention disc such as CPRM (step 714 c); and, if thedisc is not a copy prevention disc, the contents are reproduced asrecorded (step 714 d). If the disc is a copy prevention disc, the BCAidentifier 712 in the control data is read in the step 714 e.Alternatively, when the BCA identifier 712 in the control data (step 714e) does not indicate the presence of BCA (step 714 f), the BCA is notreproduced (step 714 g). At this time, from the BCA area of the RAM disc856, the information in BCA including the ID 857 is reproduced by thePE-RZ demodulation part of the BCA reproduction part 820 (step 714 n).After reading the control data 710 in which the physical properties ofthe disc 702 are recorded (step 714 h), the disc type identifier 711(step 714 h) judges whether the disc is DVD-ROM, DVD-RAM, DVD-RW, orDVD-R. If the disc is DVD-RW or DVD-R (step 714 j), the polarity of thecode in the data is reversed by the polarity reversing part 820 b of thePE-RZ demodulation part 820 a (step 714 k). In other words, if thereproduced modulated signal is “01,” the output data is demodulated to“1”, and if the reproduced modulated signal is “10”, the output data isdemodulated to “0”. Thus, it is demodulated to be the opposite ofDVD-ROM (step 714 m). The main data is demodulated by the 8-16demodulator 865 a of the data reproduction part 865. First, the keygroup 700 including a plurality of keys is reproduced from the key blockarea 919; a key suitable for this device is selected by the keyselection part 703; the key is decoded in the cryptographic decoder 708to reproduce the “first key”. This ID 857 and the above-mentioned “firstkey” are calculated in the operation part 704 to generate the “secondkey” (step 714 p). Up to this point, the procedure is the same with therecording mode of the contents. The reproduction mode of the encryptedcontents differs in that the “encrypted contents key” is reproduced anddecrypted from the disc 856, and the encrypted contents are decrypted.The flow of the reproduction-only will be explained in detail withdotted lines in FIG. 23.

The “encrypted contents key 713” that is recorded in the recording area702 of the disc 856 is reproduced in the data reproduction part 865,which is then decrypted in the cryptographic decoder 714 by using the“second key” described above, thereby decoding the contents key 715(step 714 q). This contents key is used as the decryption key to decryptthe “encrypted contents” in the cryptographic decoder 863 (step 714 r),and a plaintext 864 of the m-th contents is output (714 s). In the casewhere the data are copied regularly in only one disc, one of thecontents keys recorded and encrypted in the RAM disc forms a counterpartto the disc ID, and the code is decrypted or descrambled correctly, sothat the plaintext 864 of the m-th contents is output. With regard topicture information, MPEG signals are expanded to obtain picturesignals.

In this case, the disc ID is the key of encryption. Since the ID numberis administered and generated such that only one disc ID exists in theworld, the effect that copying the data is possible to only one RAM disccan be obtained. The principle will be explained below.

Here, it is prohibited to copy the data from the RAM disc that isinitially copied regularly to another RAM disc. However, if theencrypted contents are bit copied illegally in the original state, thedisc ID for the first disc (ID1) and the disc ID for the other RAM disc,i.e. the illegally copied disc (ID2), have different numbers. When theBCA of the illegally copied RAM disc is reproduced, the ID2 isreproduced. However, the contents and/or the title key are encryptedwith the ID1, so that the attempt to release the data with the ID2 inthe cryptographic decoder 863 fails. Namely, the title key or the codeof the contents is not decrypted correctly because the keys aredifferent. In this way, the signals of the illegally copied RAM disccannot be output, and the copyright is protected. Since the presentinvention operates according to the Disc ID system, as for a regular RAMdisc that is copied regularly for only once, the code can be released byusing any drive, which is highly convenient. In this case, theencryption part 859 may be a key administration center in a remote placeor an IC card mounted with a cryptographic encoder. Alternatively, theencryption part 859 may be included in the recording/reproductiondevice.

In the case where BCA is recorded by an initializer, the BCA cannot beerased with the drives available on the market, but it is possible for auser to obtain a recording disc without BCA and to record BCA therein.To deal with this problem, the present invention has the followingadvantage: the BCA identifier 712 is recorded by a pre-pit in thecontrol data 710 of the original board, so that the BCA identifier 712of the disc in which BCA is not recorded indicates “0”, i.e. none, andthe disc cannot be tampered with due to the pre-pit. As a result, evenif BCA is recorded illegally in this RAM disc without BCA recordafterwards, the BCA identifier cannot be tampered with, so that thereproduction device judges the disc illegal and does not operate.

The above embodiments use a rewritable phase change type optical discand are described by referring to the case in which the recording layerof the subsidiary information area and the recording layer of the maininformation area are the same. However, the present invention alsoincludes the cases in which only the part where the mediumidentification information is recorded is changed in the recording layerto have a different material composition (for example, to reduce therecording sensibility), only the part where the medium identificationinformation is recorded is changed in the recording layer to have adifferent material (for example, to apply a pigment type material), therecording layer is removed only in the part where the mediumidentification information is recorded and only the reflective layer ispresent, and the like.

Furthermore, the present invention can be applied also to aconfiguration using materials such as a magnet-optical material or apigment material for the recording layer besides the phase changematerial.

INDUSTRIAL APPLICABILITY

As described above, the present invention has the advantage of stablyrecording medium identification information to an optical recordingmedium. In particular, the initialization of the phase change typeoptical recording medium and the recording of the medium identificationinformation can be performed at the same time. Thus, the productionprocess can be simplified, and the production costs can be reduced.

1. A recording method for an optical recording medium, for recordingmedium identification information for optically distinguishing themedium by using an optical recording medium provided with a maininformation area capable of recording an information signal and asubsidiary information area for recording subsidiary information that isdifferent from the information signal, which are divided in a radialdirection of a disc-shaped substrate, wherein an information layer forrecording the information signal in the main information is providedalso in the subsidiary information area, and by emitting a light beam toform a light spot to the information layer of the subsidiary informationarea, the method comprising recording the medium identificationinformation in the information layer of the subsidiary information areaby scanning the light beam in a manner such that a previously scannedlight spot partially overlaps the light spot adjacent thereto in atangential direction of the optical recording medium and a previouslyscanned light spot adjacent thereto in a radial direction of the opticalrecording medium.
 2. The recording method of an optical recording mediumaccording to claim 1, wherein, after medium identification informationis recorded, a phase of the main information area is changedcontinuously to a crystal state for initialization.
 3. The recordingmethod of an optical recording medium according to claim 1, wherein apower of a light beam to be emitted to the information layer forrecording the medium identification information is reduced to be lowerthan a power of a light beam to be emitted to the information layerother than the medium identification information.
 4. The recordingmethod of an optical recording medium according to claim 1, wherein aconstituent material of the information layer in the main informationarea and a constituent material of the information layer in thesubsidiary information area are the same.
 5. The recording method of anoptical recording medium according to claim 1, wherein the opticalrecording medium is a disc-shaped medium, and an amount of unevendistribution of the information layer in the subsidiary information areais larger in a vicinity of an end side of a back part in a rotationdirection of the subsidiary information area where the mediumidentification information is recorded than in a vicinity of an end sideof a front part in a rotation direction of the subsidiary informationarea in the rotation direction.
 6. The recording method of an opticalrecording medium according to claim 1, wherein the optical recordingmedium is a disc-shaped medium, and the subsidiary information area islocated along an inner boundary of the main information area of thedisc-shaped medium.
 7. The recording method of an optical recordingmedium according to claim 6, wherein the subsidiary information area ispresent in the range between 22.3 mm and 23.5 mm from the center of thedisc.
 8. The recording method of an optical recording medium accordingto claim 6, wherein recording is carried out with an additional area(Burst Cutting Area) overwritten in the information layer of a pittedarea in the subsidiary information area such that either an amorphousstate is to remain in a stripe form or a crystal state is to remain in astripe form in the subsidiary information area.
 9. The recording methodof an optical recording medium according to claim 1, wherein informationsignal is recorded in the main information area with a modulation methodthat is different from a light beam modulation method used for recordingthe medium identification information.
 10. An optical recording mediumprovided with a main information area capable of recording aninformation signal and a subsidiary information area for recordingsubsidiary information that is different from the information signal,which are divided in a radial direction of a disc-shaped substrate,wherein an information layer for recording the information signal in themain information is provided also in the subsidiary information area,and an amount of uneven distribution of the information layer in thesubsidiary information area is larger in a vicinity of an end side of aback part in a rotation direction of the subsidiary information areawhere medium identification information for distinguishing the mediumoptically is recorded in the information layer of the subsidiaryinformation area than in a vicinity of an end side of a front part in arotation direction of the subsidiary information area in the rotationdirection.
 11. The optical recording medium according to claim 10,wherein medium identification information is recorded by partiallyoverlapping in the information layer of a pitted area formed in thesubsidiary information area.
 12. The optical recording medium accordingto claim 10, wherein medium identification information is recordedwithout changing the shape of the information layer in the subsidiaryinformation area.